A sentence or sentences posted on the Internet are sometimes used as information for another person to make a decision. For example, product reviews written by users who have used a product serve as information to make a decision for another user who is about to decide a product to purchase.
The system that manages product information using posting by users is disclosed in Patent literature 1 below. For example, this system receives product use information (posting of comments and the like) from a user's terminal and authenticates whether the user is a purchaser of a product related to the posting.